What is Phentermine?
Phentermine (Adipex-P, Lomaira) is an amphetamine-like prescription medication used to suppress appetite. It can help weight loss by decreasing your hunger or making you feel full longer. Phentermine is also available in combination with topiramate for weight loss (Qsymia).

Like other prescription weight-loss drugs, phentermine is intended to be used as part of an overall weight-loss plan. It is indicated for people who are obese, and who have failed to lose enough weight with diet and exercise alone — not for people who want to lose just a few pounds.

Phentermine, whose chemical name is phenyl-tertiary-butylamine, is a Schedule – IV prescription drug that is used in conjunction with diet and exercise for the treatment of obesity. It is a controlled substance and can only be issued on a prescription because of its similarities to amphetamine.

This drug was approved in the United States for medical use in 1959 and has become one of the most popular drugs for weight loss across the world. Over 7 million prescriptions are written every year. Today, phentermine is available under the brand names Lomaira, Adipex-P, Suprenza, etc.

Phentermine has also been combined with other weight loss drugs since the 1990s, of which the most commonly used is Qsymia.

How Does Phentermine Work?

Phentermine is an anorectic drug, which means it is an appetite suppressant. The drug stimulates the release of chemicals, or neurotransmitters, in the brain. The neurotransmitters whose levels are increased by this drug are norepinephrine, dopamine and serotonin.

With the increase in the levels of these chemicals in your brain, you feel full and therefore eat less. Over time, this can lead to weight loss, especially if accompanied by a proper diet and exercise.

Phentermine side effects: How does phentermine work for weight loss?

Phentermine should only be used for short-term use (less than 12 weeks at a time) to help with weight loss. It works by activating your sympathetic (“fight or flight”) nervous system, so it’s called a “sympathomimetic” drug or “stimulant.”

Phentermine may help lower your appetite, so people who take phentermine tend to eat less. This can lead to an energy deficit (meaning you are burning more calories than you are eating) and potential weight loss.

If you have obesity (or overweight with health-related complications) and intensive lifestyle changes have not helped you to lose weight, phentermine may be an option for you.

However, since there are risks associated with taking phentermine, the decision to start this medication is made on an individual basis and you should discuss it thoroughly with your healthcare provider.

How much weight will I lose with phentermine?

This depends on how much excess weight you have and how well you are able to adjust your diet while taking phentermine.

There are two studies that directly address this question:

One small study from South Korea showed that almost 86% of people who have overweight or obesity taking phentermine for 14
weeks lost more than 5% of their body weight.

Another South Korean study looked specifically at people who have obesity (not overweight) and used phentermine for a 12-week course. It found that almost 96% of them lost more than 5% of their body weight, and 62% of the same group lost more than 10% of their body weight.

Phentermine is sometimes used in combination with another medication,topiramate. Qsymia (phentermine/topiramate) is a combination medication that is approved for a longer period of time.

A large study found that 75% of people taking phentermine/topiramate over a year lost at least 5% of their body weight, compared to 23% of people taking a placebo.

What’s the typical dose for phentermine?

The typical dose of phentermine is 37.5 mg (one tablet) by mouth daily. This can be given in one dose or divided into two doses (one in the morning and one at night). Recently, a new formulation of phentermine (Lomaira) became available in smaller 8 mg doses, which can be given up to three times per day.

Due to potential risks and side effects, you should try to be on the lowest dose of phentermine that is effective for you for the shortest amount of time possible (the lowest dose that allows you to successfully lose weight).

Phentermine is a Schedule IV drug, a classification given to drugs that have a potential for abuse, although the actual potential appears to be low.

Common side effects of phentermine include:

Increased heart rate

Tingling or prickling feeling in hands or feet

Dry mouth

Sleeplessness

Nervousness

Constipation

Although phentermine is one of the most commonly prescribed weight-loss medications, it isn't a good option if you have

heart disease, high blood pressure, an overactive thyroid gland or glaucoma. It also isn't for women who are pregnant, may become pregnant or are breast-feeding.

Who shouldn’t take phentermine?

Phentermine shouldn’t be used by people with certain health conditions or statuses, including:Heart disease, including heart failure, coronary artery disease, or prior stroke

High blood pressure that’s uncontrolled

Hyperthyroidism (too much thyroid hormone)

Glaucoma (high eye pressure)

High levels of nervousness or anxiety

History of drug misuse

Pregnancy

Nursing (breastfeeding)

Allergies to other similar stimulant medications